1. Field of the Invention
The present invention relates generally to an improvement in or relating to the freight carrier's construction, and more particularly to an improved hull construction of a freight carrier for the high temperature and/or cryogenic freight in the form of a cryogenic liquefied gas such as methane, ethylene, propane, butane, ammonium and the like, and in the form of a high temperature liquid or powder material such as coal/heavy oil compound fuel, heavy oil, asphalt, sulfur, clinker, and the like.
2. Description of the Prior Art.
It is generally known that when loading such a high temperature or cryogenic freight material immediately into contact with the cargo room or storage structure incorporated in the hull of a freight carrier of, for instance, the dual shell construction, it is difficult technically to have such freight material insulated properly from the hull structure of a freight carrier, and that the hull structure is generally subjected to an excessive extent of thermal stress under the effect of a high or low temperature of the freight material while being stored therein. It has therefore been the practice, in the attempt to cope with such problem, to provide an additional insulated tank construction to the hull structure of a vessel in the inside thereof, into which the high or low temperature freight material is loaded and stored, accordingly.
While the tank or storage construction to be incorporated in the hull structure of a freight carrier is generally of the square type in practice, this type tank structure cannot be exempted from shortcomings such as the number of tank structural components being increased, the tank structure being voluminous and weighty, the working man-hours being greater, and the like.
On the other hand, while there has been proposed for use the tank structure of the spherical type, in the attempt to overcome such problems in the incorporated tank design as noted above, which is held by using the tank skirt extending along the equator line of the spherical shape thereof, it is generally known that this tank structure cannot be relieved from the such drawbacks as follows.
(1) An undesired small ratio of an interior volume of a tank versus a given volume allowable for the tank structure in the hull compartment area of a carrier, which would then result in an inferior volume efficiency.
(2) The combined weights of a freight material and a tank proper might generally be concentrated upon a tank skirt structure, which would undersirably result in a weighty tank construction in order to cope with the concentrated weight of the tank structure.
(3) Owing to the requirement in tank design that the upper end of a tank skirt structure exists along the equator line of the spherical configuration of a tank, the location of a tank skirt structure is necessarily relatively higher depending on a radius of the spherical tank configuration. In this connection, the tank skirt structure cannot generally be designed to be lowered in order to shorten the height of the tank skirt structure.
As the alternative of these square tank and the spherical tank, an upright cylindrical tank was proposed, and some vessels mounted with such cylindrical tanks have actually been constructed. However, those vessels mounted with the cylindrical tanks had the drawbacks as compared with those mounted with the spherical tanks as follows:
(1) The size of the hull for ensuring the same tank capacity failed to be reduced. In other words, as compared with the size of the hull, large tank capacity failed to be ensured.
(2) The surface area per volume of the tank becomes increased, and as a result, the conventional cylindrical tank system remains unprevailed.
In consideration of such drawbacks particular to the conventional tank structures of square or spherical types as well as conventional cylindrical type as noted above, it has long been a desire to attain an efficient resolution for overcoming such inevitable shortcomings in the design of a tank structure to be incorporated in the hull construction of a freight carrier with a limited space.
The present invention is essentially directed to the provision of a due and proper resolution to such inconveniencies and difficulties in practice as outlined above and experienced in the conventional tank structure designs of square and spherical types as well as conventional cylindrical type which have been left unattended with any proper countermeasures therefor.